Patent GB-782626-A (GB)
Title: Improvements in hydro-pneumatic suspension units for motor vehicles
IPC: B60G17/044
Filed: 1956-03-29
Abstract: 782,626. Road-vehicle spring-suspensions; pneumatic springs. GENERAL MOTORS CORPORATION. March 29, 1956 [April 11 , 1955; April 26, 1955]. No.' 10016/56. Classes 108(2) and 108(3) A hydro-pneumatic suspension unit comprises a piston 25 and cylinder 20 surrounded by an outer housing 26 to form an annular space 30 divided by an expansible wall 27 into two independent chambers 28, 29, filled respectively with hydraulic fluid and gas under pressure, the chamber 28 being connected through valves 62, 65, to one end of the cylinder 20, the piston 25 having a rod 40 which extends through the other end of the cylinder 20. As shown, the wall 27 comprises a tubular member of rubber clamped to respective ends of the housing 26 by closure members 45, 53 of the housing 26. A tubular member 71 defines within the hollow piston rod 40, an annular liquid reservoir space 77 which is connected by ports 128 and a spring loaded valve 125 with the interior. of the member 71. A tubular pump plunger 115 is rigid at its upper end with the closure member 45 and extends through a seal ring 117 in.the piston 25, into the interior of the tubular member 71. The interior of the member 115 communicates at its upper end via a passage 123 with the cylinder space 31 above the piston 25..The lower end of the member 115 is in communication with the interior of the member 71 via a check valve 121. The upper part of the tubular member 71 above a bearing sleeve 120 for'.the pump member 115 is in communication with the interior of the member 115 via ports 130. The uppermost end of the interior of the tubular member 71 is connected by a passage 134 with the housing 105 of a ball valve 102 which is normally held in closed position by a spring 103. The ball valve 102 is adapted to be. unseated by the action of a pin 101 when it is engaged by the retainer 90 of a diaphragm 84. The retainer 90 is connected by pins 85 to the abutment 86 of a coiled spring 95, the other end of which is in abutment with the lower end of the cylinder 20. Movement of the retainer 90 is retarded by the dashpot action of .liquid enclosed in a chamber 100 defined by the diaphragm 84 and a spacer member 81 of the piston 25. Liquid in the chamber 100 displaced by the upward movement of the pins 85, and thus of the diaphragm 84, has to pass through a restricted orifice 107 and a restricted passage 109 leading via a channel 110 to the reservoir 77. The lower end of the piston rod 40 is connected to a lower wish-bone link of an independent front suspension and the closure member 34 is connected to a vehicle frame member near to the pivotal connection of an upper wish-bone link (Fig. 1, not shown). In operation, on upward movements of the vehicle wheel, .the piston 25 is forced forced upwardly from a normal position mid-way along the length of the cylinder 20, to force liquid from the cylinder space 31 through valve 62 to the space ,28 against air pressure in the space 29 acting on the expansible wall 27. Liquid in the interior of the lower part of the tubular member 71 is forced by the pump .member 115 into the interior of the latter and thence to the cylinder space 31. As subsequent upward deflections of the wheel, and thus of the piston 25 occur, more liquid is forced by the action of the pump member 115 into the cylinder space 31, and this has the effect of-gradually driving down the mean position of the piston 25. When the latter reaches a predetermined point, the compression of the spring 95 is such as to react on the pins 85 to cause lifting of the pin 101 and thus opening of the valve 102. Liquid is then able to escape from the chamber 31 via the interior of the pump tube 115, ports 130, passage 134, valve 102, chamber 100, restricted orifice 107, restricted passage 109, and channel 110, to the reservoir 77. Thus when the height of the vehicle tends to rise or drop relative to the ground under a change in static load, the action of the pump member 115 and cylinder 71 in conjunction with the valve 102 is such as to bring the position of the piston 25 and thus the height of the vehicle back to a predetermined position. In a simpler modification (Fig. 2, not shown), the pump member 115, valve 102 and associated mechanism, are dispensed with, the piston rod being solid.